--- a/xpcom/glue/nsQuickSort.cpp
+++ b/xpcom/glue/nsQuickSort.cpp
@@ -99,80 +99,79 @@ void NS_QuickSort (
 	void *a,
 	unsigned int n,
     unsigned int es,
 	cmp_t *cmp,
 	void *data
     )
 {
 	char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
-	int d, r, swaptype, swap_cnt;
+	int d, r, swaptype;
 
 loop:	SWAPINIT(a, es);
-	swap_cnt = 0;
+	/* Use insertion sort when input is small */
 	if (n < 7) {
 		for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
 			for (pl = pm; pl > (char *)a && cmp(pl - es, pl, data) > 0;
 			     pl -= es)
 				swap(pl, pl - es);
 		return;
 	}
+	/* Choose pivot */
 	pm = (char *)a + (n / 2) * es;
 	if (n > 7) {
 		pl = (char *)a;
 		pn = (char *)a + (n - 1) * es;
 		if (n > 40) {
 			d = (n / 8) * es;
 			pl = med3(pl, pl + d, pl + 2 * d, cmp, data);
 			pm = med3(pm - d, pm, pm + d, cmp, data);
 			pn = med3(pn - 2 * d, pn - d, pn, cmp, data);
 		}
 		pm = med3(pl, pm, pn, cmp, data);
 	}
 	swap(a, pm);
 	pa = pb = (char *)a + es;
 
 	pc = pd = (char *)a + (n - 1) * es;
+	/* loop invariants:
+	 * [a, pa) = pivot
+	 * [pa, pb) < pivot
+	 * [pb, pc + es) unprocessed
+	 * [pc + es, pd + es) > pivot
+	 * [pd + es, pn) = pivot
+	 */
 	for (;;) {
 		while (pb <= pc && (r = cmp(pb, a, data)) <= 0) {
 			if (r == 0) {
-				swap_cnt = 1;
 				swap(pa, pb);
 				pa += es;
 			}
 			pb += es;
 		}
 		while (pb <= pc && (r = cmp(pc, a, data)) >= 0) {
 			if (r == 0) {
-				swap_cnt = 1;
 				swap(pc, pd);
 				pd -= es;
 			}
 			pc -= es;
 		}
 		if (pb > pc)
 			break;
 		swap(pb, pc);
-		swap_cnt = 1;
 		pb += es;
 		pc -= es;
 	}
-	if (swap_cnt == 0) {  /* Switch to insertion sort */
-		for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
-			for (pl = pm; pl > (char *)a && cmp(pl - es, pl, data) > 0;
-			     pl -= es)
-				swap(pl, pl - es);
-		return;
-	}
-
+	/* Move pivot values */
 	pn = (char *)a + n * es;
 	r = XPCOM_MIN(pa - (char *)a, pb - pa);
 	vecswap(a, pb - r, r);
 	r = XPCOM_MIN<size_t>(pd - pc, pn - pd - es);
 	vecswap(pb, pn - r, r);
+	/* Recursively process partitioned items */
 	if ((r = pb - pa) > (int)es)
         NS_QuickSort(a, r / es, es, cmp, data);
 	if ((r = pd - pc) > (int)es) {
 		/* Iterate rather than recurse to save stack space */
 		a = pn - r;
 		n = r / es;
 		goto loop;
 	}